This proposal seeks support jointly for the 2014 Gordon Research Conference (GRC) and associated Gordon Research Seminar (GRS) on Photo sensory Receptors and Signal Transduction, to be held in Il Ciocco, Italy, on April 5-6 (GRS) and April 6-11, 2014 (GRC). This GRC has regularly attracted researchers from across the world. About half of participants will be from the USA and half from Europe, the Far East and South America, thus reflecting the active international community in this scientific area. Researchers will present and discuss the fundamental topics of photobiology: How detection of light by molecular photoreceptors leads to structural changes in the photoreceptors themselves; how these changes propagate through signaling networks and across boundaries between cells to effect physiological changes at the cellular level; and ultimately, how the behavior of an organism is modified. Although photobiology largely originated in the plant sciences and is still vigorously represented there, it now embraces other experimental organisms such as bacteria, fungi, birds and humans. The fields spans disciplines from biophysics and molecular biology through cellular and organismal physiology, and has very recently come to include clinical medicine. A highly applied component has recently emerged in which light is used as an active tool to modify the behavior of an organism, under the title of optogenetics. Thus, the fast-moving field of optogenetics spans the range from molecular to clinical, with practitioners developing, for example, molecular methods aimed at modifying the transmission of nerve impulses and the restoration of vision. The topics to be presented and discussed thus span the full range of objectives of the National Eye institute of the NIH and in particular, culminate in very rapidly developing aspects of its clinical mission. Scientists studying disparate organisms speak different scientific languages, apply quite distinct experimental approaches to explore different levels of problems, and usually meet in separate conferences that tend to focus on one discipline, organism or mode of attack. Here, a major goal of this GRC is to unite the disciplines in vigorous discussion with each other. The closely-associated GRS will allow students, postdocs and junior researchers to present their recent work in this field, lay the scientific groundwork for fields they may be less familiar with, and offer explicit mentoring led by senior scientists in informal, round-table discussions aimed at broad aspects of career development.